Hi folks. I had a strange thing happen to me and I was wondering if some of you physics gurus could explain it to me. It's my understanding that gas escaping from a pressurized tank makes things cooler. In fact I recently had to empty my scuba tanks for transport and the valves did indeed ice up as the air escaped. However the other day I found a helium tank it my garage. This is the cheap non-refillable kind you get from toys-r-us for blowing up balloons. It has two valves. A metal one you turn and then a rubber nozzle you put the balloon over and hold sideways to blow up the balloon. My four year old son was standing next to me so I decided to blow up a balloon for him. I turned the metal valve a bit, put a balloon over the nozzle and pushed it sideways. In a couple seconds the thing got so hot it actually burned my thumb and I had a blister for a few days. How could this happen?